1. Field of the Invention
The present invention relates to a method of fabricating a bow stick of a stringed instrument, and a bow stick of a stringed instrument.
2. Description of Related Art
Conventionally, wooden bow sticks (sticks) have been used for a bow of a stringed instrument such as a violin, a viola, a cello, or a contrabass. Among these, Pernambuco wood, which is hard with a high density, resistant to moisture, and has superior bending strength, has been used as a material suitable for a bow stick. However, Pernambuco wood availability has greatly decreased due to felling of trees and it has been difficult to get Pernambuco wood due to the recent international trade restrictions.
Therefore, as a substitute for a bow stick formed of a wood such as Pernambuco wood, a bow stick formed of fiber-reinforced plastics (FRP) using a composite material of a fiber and a resin, such as carbon fiber-reinforced plastics (CFRP) or glass fiber-reinforced plastics (GFRP) has been developed (for example, see Japanese Patent Granted Publication No. S44-19189).
Since a wooden bow stick is cut out from timber and is manually finished, completely-equal sticks cannot be fabricated. However, since an FRP bow stick is fabricated using the same material and mold, industrially-equal sticks can be fabricated with excellent reproducibility. When a wooden bow stick is fabricated, it is difficult to adjust, for example, a weight distribution, a center of gravity, and a weight of a bow stick without changing the outer shape or size, due to a difference in density of wood as a natural material.
As a method of fabricating a hollow fiber-reinforced resin molded product, a method which is called an internal pressure molding method is known (for example, see Japanese Unexamined Patent Application, First Publication No. H11-48318). In the internal pressure molding method, prepreg in which a fiber is impregnated with a non-cured resin is wound on a pressurizing bag formed of a flexible material and the resultant is set in a mold. Then, the mold is clamped and is then heated while inflating the pressurizing bag to push the prepreg into the inner surface of the mold. As a result, the prepreg can be shaped into a shape corresponding to the cavity formed between the mold and the pressurizing bag.
However, in the method of fabricating a hollow fiber-reinforced resin molded product using the internal pressure molding method, since the prepreg moves in the mold when swelling the pressurizing bag, the swelling of the pressurizing bag may be uneven.
Therefore, when a bow stick is fabricated using the internal pressure molding method, the shape of the cavity is not constant every molding and the weight distribution or the center of gravity of a bow stick to be molded is uneven.
On the other hand, the inventors of the present invention proposed a method of molding a hollow-structured product, in which an FRP prepreg is wound around a columnar metal mandrel having a tapered end and capable of springing back, the mandrel around which the FRP prepreg is wound is set into a mold having the outer portion of the hollow-structured product as a cavity, the mold is heated to acquire a molded product, and then the mandrel is removed therefrom (for example, see Japanese Patent No. 3541756).
When a bow stick is fabricated using the method of molding a hollow-structured product, the shape of the cavity formed between the mold and the mandrel can be kept even every molding at the time of molding. Therefore, it is possible to prevent unevenness in the weight distribution or the center of gravity of molded bow sticks.
Tastes of users (stringed instrument players') differ depending on a slight difference in the weight distribution, the center of gravity, the weight, and the like of the bow stick of a stringed instrument. Accordingly, when a bow stick formed of the FRP is fabricated, plural bow sticks which are finely adjusted in the weight distribution, the center of gravity, the weight, and the like of the bow sticks on the basis of tastes of the users need to be prepared.